A method of pre-compensating for transmitter in-phase (I) and quadrature (Q) mismatch (IQMM) may include sending a signal through an up-converter of a transmit path to provide an up-converted signal, determining the up-converted signal, determining one or more IQMM parameters for the transmit path based on the determined up-converted signal, and determining one or more pre-compensation parameters for the transmit path based on the one or more IQMM parameters for the transmit path. In some embodiments, the up-converted signal may be determined through a receive feedback path. In some embodiments, the up-converted signal may be determined through an envelope detector.
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4. A method of pre-compensating for transmitter in-phase (I) and quadrature (Q) mismatch (IQMM), the method comprising:
sending a first input signal at a first frequency through a transmit path to provide a first output signal;
sending a second input signal at a second frequency through the transmit path to provide a second output signal;
sending the first output signal through an envelope detector to provide a first output of the envelope detector;
sending the second output signal through the envelope detector to provide a second output of the envelope detector;
determining one or more IQMM parameters for the transmit path based on the first output of the envelope detector and the second output of the envelope detector; and
determining one or more pre-compensation parameters for the transmit path based on the one or more IQMM parameters for the transmit path.
1. A method of pre-compensating for transmitter in-phase (I) and quadrature (Q) mismatch (IQMM), the method comprising:
sending a first signal through a transmit path to provide a second signal;
sending the second signal through an envelope detector;
determining one or more IQMM parameters for the transmit path based on an output of the envelope detector; and
determining one or more pre-compensation parameters for the transmit path based on the one or more IQMM parameters for the transmit path;
wherein determining the one or more IQMM parameters for the transmit path comprises:
applying a first pre-compensation parameter to the transmit path;
determining a first power of a component of the second signal caused by transmit IQMM through the envelope detector based on the first pre-compensation parameter;
applying a second pre-compensation parameter to the transmit path;
determining a second power of a component of the second signal caused by transmit IQMM through the envelope detector based on the second pre-compensation parameter; and
selecting one of the first pre-compensation parameter or the second pre-compensation parameter based on a lower of the first power and the second power.
3. A method of pre-compensating for transmitter in-phase (I) and quadrature (Q) mismatch (IQMM), the method comprising:
sending a first signal through a transmit path to provide a second signal;
sending the second signal through an envelope detector;
determining one or more IQMM parameters for the transmit path based on an output of the envelope detector; and
determining one or more pre-compensation parameters for the transmit path based on the one or more IQMM parameters for the transmit path;
wherein determining the one or more IQMM parameters for the transmit path comprises:
applying a first pre-compensation parameter to the transmit path;
determining a first power of a component of the second signal caused by transmit IQMM through the envelope detector based on the first pre-compensation parameter;
applying a second pre-compensation parameter to the transmit path; and
determining a second power of a component of the second signal caused by transmit IQMM through the envelope detector based on the second pre-compensation parameter;
the method further comprising:
sweeping a frequency of the first signal sent through the transmit path to provide one or more additional second signals;
sending the one or more additional second signals through the envelope detector to provide one or more additional outputs of the envelope detector; and
determining the one or more IQMM parameters for the transmit path based on the one or more additional outputs of the envelope detector.
2. The method of
the method further comprises:
applying one or more additional pre-compensation parameters to the transmit path; and
determining one or more additional powers of one or more components of the second signal caused by transmit IQMM through the envelope detector based on the one or more additional pre-compensation parameters; and
determining the one or more IQMM parameters for the transmit path comprises selecting one of the first pre-compensation parameter, the second pre-compensation parameter or the one or more additional pre-compensation parameters based on a lower of the first power, the second power, or the one or more additional powers.
5. The method of
6. The method of
determining the one or more IQMM parameters for the transmit path comprises solving a system of equations based on the first and second output signals; and
a first one of the equations comprises a function, at least in part, of the first and second pre-compensation parameters.
7. The method of
8. The method of
sweeping the first and second frequencies for each of the first and second pre-compensation parameters;
determining additional first and second output signals based on sweeping the first and second frequencies; and
determining the one or more IQMM parameters for the transmit path over frequency based on the determined additional first and second output signals.
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This application is a continuation of U.S. patent application Ser. No. 17/092,214 filed Nov. 6, 2020 which is incorporated by reference and which claims priority to, and the benefit of, U.S. Provisional Patent Application Ser. No. 63/025,980 titled “Transmitter Frequency-Dependent In-Phase and Quadrature Mismatch Calibration” filed May 15, 2020 which is incorporated by reference.
This disclosure relates generally to quadrature transmitters, and more specifically to transmit IQ mismatch calibration.
A quadrature transmitter may include an in-phase (I) path and a quadrature (Q) path. Imbalances between the I and Q paths, which may be referred to as IQ mismatch (IQMM), may degrade the performance of the transmitter.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not constitute prior art.
A method of pre-compensating for transmitter in-phase (I) and quadrature (Q) mismatch (IQMM) may include sending a signal through an up-converter of a transmit path to provide an up-converted signal, determining the up-converted signal through a down-converter of a receive feedback path, determining one or more IQMM parameters for the transmit path based on the determined up-converted signal, and determining one or more pre-compensation parameters for the transmit path based on the one or more IQMM parameters for the transmit path. Determining one or more IQMM parameters for the transmit path may include solving a system of equations, a rust one of the equations may include a first component of the up-converted signal and a first parameter representing, at least in part, a desired frequency response of the transmit path, and a second one of the equations may include a second component of the up-converted signal and a second parameter representing, at least in part, a frequency response of the transmit path due to transmit IQMM. The first one of the equations may further include a third parameter representing, at least in part, a gain and delay for the transmit path. The method may further include determining an IQMM for the receive feedback path by using a first local oscillator for the transmit path and a second local oscillator for the receive path, and determining one or more IQMM parameters for the transmit path based on the determined up-converted signal may include processing the up-converted signal to compensate for the IQMM in the receive path. A local oscillator for the transmit path may have a frequency shift from a local oscillator for the receive feedback path. The signal may include a first signal at a first frequency, the up-converted signal may include a first up-converted signal, and the method may further include sending a second signal at a second frequency through the up-converter of the transmit path to provide a second up-converted signal, determining the second up-converted signal through the down-converter of the receive feedback path, and determining one or more IQMM parameters for the transmit path based on the determined second up-converted signal.
A method of pre-compensating for transmitter in-phase (I) and quadrature (Q) mismatch (IQMM) may include sending a signal through an up-converter of a transmit path to provide an up-converted signal, determining the up-converted signal through an envelope detector, determining one or more IQMM parameters for the transmit path based on the determined up-converted signal, and determining one or more pre-compensation parameters for the transmit path based on the one or more IQMM parameters for the transmit path. Determining one or more IQMM parameters for the transmit path may include applying a first pre-compensation parameter to the transmit path, determining a first power of a component of the up-converted signal caused by transmit IQMM through the envelope detector based on the first pre-compensation parameter, applying a second pre-compensation parameter to the transmit path, and determining a second power of a component of the up-converted signal caused by transmit IQMM through the envelope detector based on the second pre-compensation parameter. Determining one or more IQMM parameters for the transmit path may further include selecting one of the first pre-compensation parameter or the second pre-compensation parameter based on a lower of the first power and the second power. The method may further include applying one or more additional pre-compensation parameters to the transmit path, and determining one or more additional powers of one or more components of the up-converted signal caused by transmit IQMM through the envelope detector based on the one or more additional pre-compensation parameters, and determining one or more IQMM parameters for the transmit path may include selecting one of the first pre-compensation parameter, the second pre-compensation parameter or the one or more additional pre-compensation parameters based on a lower of the first power, the second power, or the one or more additional powers. The signal may include a first signal at a first frequency, the up-converted signal may include a first up-converted signal, and the method may further include sending a second signal at a second frequency through the up-converter of the transmit path to provide a second up-converted signal, determining the second up-converted signal through the envelope detector, and determining one or more IQMM parameters for the transmit path based on the determined second up-converted signal. The method may further include applying first and second pre-compensation parameters to the transmit path for each of the first and second signals, and the first and second up-converted signals may be determined separately based on the first and second pre-compensation parameters. Determining one or more IQMM parameters for the transmit path may include solving a system of equations based on the determined first and second up-converted signals. A first one of the system of equations may include a function, at least in part, of the first and second pre-compensation parameters. The second frequency may be a negative of the first frequency at baseband. The method may further include sweeping the first and second frequencies for each of the first and second pre-compensation parameters, determining additional first and second up-converted signals based on sweeping the first and second frequencies, and determining one or more IQMM parameters for the transmit path over frequency based on the determined additional up-converted signals. The signal may include a first two-tone signal, the up-converted signal may include a first up-converted two-tone signal, and the method may further include sending a second two-tone signal through the up-converter of the transmit path to provide a second up-converted two-tone signal, determining the second up-converted two-tone signal through the envelope detector, and determining one or more IQMM parameters for the transmit path based on the determined second up-converted two-tone signal. Determining one or more IQMM parameters for the transmit path may include solving a system of equations based on the determined first and second up-converted two-tone signals, and at least one of the equations may include a first parameter of a first frequency of the first two-tone signal and a second parameter of a second frequency of the first two-tone signal. The method may further include sweeping first and second frequencies of at least one of the two-tone signals, determining additional first and second up-converted two-tone signals based on sweeping the first and second frequencies, and determining one or more IQMM parameters for the transmit path over frequency based on the determined additional up-converted two-tone signals.
A system may include an IQ transmit path comprising an up-converter, an envelope detector arranged to provide an envelope of an up-converted signal from the IQ transmit path, a signal generator arranged to apply a pilot signal to the IQ transmit path, a signal observer arranged to capture the envelope of the up-converted signal based on the pilot signal, and a processor configured to: estimate one or more IQ mismatch (IQMM) parameters for the IQ transmit path based on the captured envelope of the up-converted signal, and estimate one or more compensation coefficients for the IQ transmit path based on the estimated IQMM parameters. The signal observer may be arranged to capture the envelope of the up-converted signal through a branch of an IQ receiver.
A system may include an IQ transmit path comprising an up-converter, an IQ receive path comprising a down-converter, a feedback connection arranged to couple an up-converted signal from the IQ transmit path to the IQ receive path, a signal generator arranged to apply a pilot signal to the IQ transmit path, a signal observer arranged to capture the up-converted signal through the IQ receive path based on the pilot signal, and a processor configured to: estimate one or more IQ mismatch (IQMM) parameters for the IQ transmit path based on the captured up-converted signal, and estimate one or more compensation coefficients for the IQ transmit path based on the estimated IQMM parameters.
The figures are not necessarily drawn to scale and elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. The figures are only intended to facilitate the description of the various embodiments disclosed herein. The figures do not describe every aspect of the teachings disclosed herein and do not limit the scope of the claims. The accompanying drawings, together with the specification, illustrate example embodiments of the present disclosure, and, together with the description, serve to explain the principles of the present disclosure.
This disclosure encompasses numerous inventive principles relating to pre-compensation for in-phase (I) and quadrature (Q) mismatch (IQMM) in quadrature up-conversion transmitters. Pilot signals may be applied at baseband to a transmit (TX) path, and the IQMM impaired up-converted signals may be captured and processed using various disclosed techniques and algorithms to estimate the TX IQMM, which may include both frequency-independent IQMM (FI-IQMM) and frequency-dependent IQMM (FD-IQMM). The estimated IQMM may then be used to determine coefficients for a pre-compensator in the TX path.
In some embodiments, the IQMM impaired up-converted signals may be captured through a receive (RX) feedback path having a quadrature down-converter. Single-tone pilot signals may be applied at different frequencies, and primary and mirror components of the captured down-converted signals may be used in a system of equations to estimate IQMM parameters for the TX path. Effects of RX IQMM in the RX feedback path may be reduced or eliminated through various disclosed techniques, for example, by using separate local oscillators for the TX and RX paths and/or a frequency shift between the local oscillators for the TX and RX paths.
In some embodiments, the IQMM impaired up-converted signals may be captured through an envelope detector and processed using various disclosed techniques. In a first method using an envelope detector, a single-tone pilot signal may be applied while varying one or more pre-compensation parameters. A single-tone pilot signal applied at baseband may produce a signal at the output of the envelope detector having a component at twice the frequency of the pilot signal if there is IQMM in the TX path. Thus, the first method may sweep one or more pre-compensation parameters while applying a first single-tone pilot signal and selecting one or more of the parameters that provide the lowest output power from the envelope detector at twice the frequency of the pilot signal. A search may be performed by repeating this process at other frequencies to select one or more parameters for each frequency. The selected parameters may then be used to estimate IQMM parameters for the TX path.
In a second method using an envelope detector, one or more TX IQMM parameters for a given frequency may be estimated directly by separately sending the negative and positive frequencies of a single-tone pilot signal at baseband using two different sets of pre-compensator settings. The components at twice the given frequency at the output of the envelope detector may be combined in a set of equations and solved for the frequency-dependent gain and phase mismatch at the given frequency. This process may be repeated to determine the frequency-dependent gain and phase mismatch at other frequencies, which may then be used to estimate the IQMM parameters for the TX path.
In a third method using an envelope detector, various combinations of the negative and positive frequencies of two-tone pilot signals may be applied separately to the TX path at baseband. The outputs of the envelope detector at various frequencies may be combined and solved using a set of equations to obtain estimates of the TX IQMM parameters directly.
Once TX IQMM parameters are determined by any of these disclosed techniques, they may be used to determine coefficients for a pre-compensator in the TX path.
The principles disclosed herein may have independent utility and may be embodied individually, and not every embodiment may utilize every principle. Moreover, the principles may also be embodied in various combinations, some of which may amplify benefits of the individual principles in a synergistic manner.
In quadrature up-conversion transmitters. IQMM between the I and Q branches may create interference between the mirror frequencies after up-conversion to radio frequency (RF) or intermediate frequency (IF). Thus, the IQMM may degrade system performance by reducing the effective signal-to-interference-plus-noise ratio (SINR). Frequency-independent IQMM (FI-IQMM) may originate from imbalances at mixers, while frequency-dependent IQMM (FD-IQMM) may be caused by mismatch between overall frequency responses on the I and Q paths. In some embodiments, only frequency-independent IQMM (FI-IQMM) may be compensated. However, in some applications such as wideband systems (e.g., mmWave systems). FI-IQMM compensation alone may not provide adequate performance. Thus, some of the inventive principles of this application relate to techniques for providing FD-IQMM compensation for quadrature up-converter transmitters. Moreover, TX IQMM may be different than RX IQMM. Therefore, in some embodiments, calibration methods for a TX path according to this disclosure may be different than that those for an RX path.
In the transmitter, gTX≠1 and ϕTX≠0 may denote the TX gain and phase mismatches, respectively, that may create frequency-independent IQ mismatch (FI-IQMM) at the transmitter. The mismatch between the overall frequency responses hITX(t) and hQTX(t) in the I and Q paths of the TX path may create FD-IQMM in the TX path, that is, hITX(t)≠hQTX(t).
The baseband equivalent of the upconverted signal in the TX path 100 (at the output of the mixers) in the frequency-domain may be given by
ZTX(f)=G1TX(f)U(f)+G2TX(f)U*(−f), (1)
where U(f) may be the frequency response of the desired baseband (BB) signal at the input of the analog baseband (ABB) filters 108 and 110 in the TX path, and G1TX(f) and G2TX(f) may be defined as
In Equations (2). HITX(f) and HQTX(f) may denote the frequency responses of filter 108 (hITX(t)) and filter 110 (hQTX(t)), respectively. In Equation (1), G1TX(f)U(f) may represent a desired TX signal, and G2TX(f)U*(−f) may represent a TX image signal. Without any IQMM, (gTX=1, ϕTX=0, and h1TX(t)=hQTX(t)), G2TX(f), and consequently, the second term in Equation (1) may become zero. Thus, In some embodiments, G1TX(f) may represent a desired frequency response of the transmit path, and G2TX(f) may represent a frequency response of the transmit path due to IQMM.
In some embodiments according to this disclosure, the effects of IQMM in the transmitter 100 may be compensated by estimating one or more IQMM parameters in the transmitter, and then using the estimated IQMM parameters to determine pre-compensation parameters.
The one or more IQMM parameters may include any parameters that may be affected by IQMM in the TX path such as gain mismatch gTX, phase mismatch ϕTX, filters hITX(t) and hQTX(t) (and/or their frequency responses HITX(f) and HQTX(f)), G1TX(f), G2TX(f), VTX(f) (as described below), and/or the like. In some example embodiments described below, the parameters ϕTX and VTX(f) may be used as the IQMM parameters because, for example, they may reduce the complexity and/or effort involved with mathematical derivations. However, other IQMM parameters may be used according to this disclosure. For example, in some example embodiments, G1TX(f) and G2TX(f) may be used as IQMM parameters which may be estimated and then used to determine pre-compensation parameters.
The pre-compensation parameters may be any parameters that may determine how the IQMM pre-compensator 118 may affect the IQMM in the TX path 100. An example of pre-compensation parameters may be coefficients for the IQMM pre-compensator 118 (IQMC coefficients) which may shape the BB signal s[n]=sI[n]+jsQ[n] so as to reduce or eliminate an image component in the upconverted signal zTX(t). Examples of IQMC coefficients that may be obtained based on estimated IQMM parameters are described below.
In some embodiments, the IQMM parameter VTX(f) mentioned above, which may depend on the TX gain and filter mismatches, may be defined as follows
Various calibration algorithms described herein may be used to estimate phase mismatch ϕTX and VTX(f) for continuous-time frequencies f=±f1, . . . , ±fK across a desired frequency band. The estimates of ϕTX and VTX(f) may then be used to obtain IQ mismatch compensator (IQMC) coefficients for the pre-compensator 118 to reduce TX FD-IQMM.
Values for coefficients for the pre-compensator illustrated in
where WTXopt(f) may denote the frequency response of filter wTX[n]. From Equation (4), it may be apparent that optimal responses of IQMC coefficients may involve knowledge of ϕTX and/or VTX(f), which may be estimated, for example, using any of the techniques disclosed herein.
In some embodiments, and depending on the implementation details, the methods, expressions, and/or the like disclosed herein may provide optimal values, and thus, the designator “opt” may be used. However, the inventive principles are not limited to embodiments in which optimal values may be obtained, and the use of “opt” or “optimal” is not limited to methods, expressions, and/or the like that may provide optimal values.
Some example embodiments of the CVC structure illustrated in
The CVC structure illustrated in
The feedback connection 304 may be implemented with any suitable apparatus such as switches, couplers, conductors, transmission lines, filters, and/or the like. The feedback connection 304 may be coupled to the TX path 300 at any location after the up-converter 314. The feedback connection 304 may be coupled to the RX path 302 at any location before the down-converter 320. In some embodiments, some or all of the feedback connection 304 may be integral with the TX path 300 and/or the RX path 302.
The TX path 300 and the RX path 302 may each include an I signal path or branch and a Q signal path or branch. The RF transmission block 316 may include various components to transmit an RF signal such as a power amplifier, a band-pass filter, an antenna, and/or the like. The RF reception block 318 may include various components to receive an RF signal such as an antenna, a band-pass filter, a low noise amplifier (LNA) and/or the like. Depending on whether the system is in an operational mode or a calibration mode. IQMM in the TX path 300 may be corrected by the IQMM pre-compensator 308.
In some embodiments, the processor 332 may manage and/or control the overall operation of the system illustrated in
Although various components illustrated in
The components of the signal processing unit 306 may be implemented with hardware, software, and/or any combination thereof. For example, full or partial hardware implementations may include combinational logic, sequential logic, timers, counters, registers, gate arrays, amplifiers, synthesizers, multiplexers, modulators, demodulators, filters, vector processors, complex programmable logic devices (CPLDs), field programmable gate arrays (FPGAs), state machines, data converters such as ADCs and DACs, and/or the like. Full or partial software implementations may include one or more processor cores, memories, program and/or data storage, and/or the like, which may be located locally and/or remotely, and which may be programmed to execute instructions to perform one or more functions of the components of the signal processing unit 306.
The RX path 402 may include an I signal path including a mixer 426, a low-pass filter 430 having an impulse response hIRX(t), and an ADC 434. The RX path 402 may also include a Q signal path including a mixer 428, a low-pass filter 432 having an impulse response hQRX(t), and an ADC 436. The mixers 426 and 428 and filters 430 and 432 may collectively form a down-converter. In some embodiments, the RX path 402 may further include an IQMM compensator (not shown) which may be disabled or placed in a pass-through state during a calibration operation.
In some embodiments, during a calibration operation. IQMM pre-compensator 418 may be disabled or placed in a pass-through mode such that IQMC may be unity, and therefore U(f)=S(f).
To estimate the IQMM parameters ϕTX and VTX(f), a single-tone signal may be applied at baseband of the TX path 400 at frequency fk, that is, U(f)=ATXδ(f−fk) where ATX may be an unknown scaling factor that may account for gain and/or delay of the path between the TX baseband signal generation and the input of the ABB filters 408 and 410. The IQMM impaired up-converted signal may be observed by capturing the frequency response of the down-converted signal through the RX feedback path at the principal and image frequencies (fk and −fk), which may be denoted by R1,kR(fk) and R2,k
R(−fk). Next, a single-tone signal at frequency −fk, that is. U′(f)=A*TXδ(f+fk), may be sent through the TX path 400, and the down-converted signal at frequencies −fk and fk may be denoted by R3,k=R′(−fk) and R4,k=R′(fk), respectively. Collecting all of the observations may provide the following set of equations
R1,k=ATXARXG1TX(fk)
R2,k=A*TXARXG2TX(−fk)
R3,k=A*TXARXG1TX(−fk)
R4,k=ATXARXG2TX(fk) (5)
where ARX may denote the gain and/or delay from the RX ABB filters 430 and 432 to the RX BB. In some embodiments, the four Equations (5) may be time-aligned for correct estimation of IQMM parameters.
The single-tone signal (e.g., fk) may be swept across the channel band for all selected frequencies to obtain estimates of ϕTX and VTX(f) using Equations (5) as follows
where
In some implementations of the calibration algorithm described above, the IQMM at the RX feedback path may be assumed to be zero. In some other implementations, the RX feedback path may introduce RX IQMM into the observations as well, which may degrade the estimation accuracy of the TX IQMM parameters.
In some embodiments, either or both of the two techniques described below may reduce or eliminate the effects of IQMM in the RX feedback path on observations of up-converted pilot signals according to this disclosure.
In a first technique according to this disclosure, RX FD-IQMC may be calibrated using separate local oscillators (LOs) for the TX and RX paths in loopback mode (e.g., sweeping the TX LO and using a DC tone at BB of the TX path while keeping RX LO fixed). Next, BB TX tones may be swept across frequency keeping both the TX LO and RX LO fixed at the same frequency. The TX FD-IQMC coefficients may then be determined. In some embodiments, an additional step may be added to post-process the received signal R(f) to remove the effect of RX-IQMM before estimation of ϕTX and VTX(f).
In a second technique according to this disclosure, a frequency shift may be created between the LOs of the TX and RX paths such that the RX-IQMM may not interfere with the principal and mirror signals of the TX path. In some embodiments, the frequency shift between the LOs may be kept relatively small, for example, to preserve the approximate symmetry of the ABB filter response that the TX principal and image signals may observe.
The system illustrated in
In some embodiments, the envelope detector 640 may provide an output having a form, for example, of y(t)=|z(t)|2. In some embodiments, some or all of the envelope detector 640 may be integral with the TX path 600.
In some embodiments, the 640 envelope detector may output the envelope of the IQMM impaired up-converted signal and feed it back to the signal processing unit 606 without going through a mixer. Thus, the captured signal may only contain TX IQMM without any RX impairments. Although the return signal path 642 is not limited to any specific implementation details, in some embodiments, either the I or Q signal path downstream of a multiplier in a quadrature receiver may be used as the return signal path. This may be convenient, for example, in a transceiver system in which the RX path already exists.
The TX path 700, which may be similar to the TX path 400 illustrated in
The RX path 702, which may be similar to the RX path 402 illustrated in
The envelope detector 740 may be connected to the TX path 700 at any location after the up-conversion unit. It may also be connected to the RX path 702 at any location after the mixers 726 and 728. In the embodiment illustrated in
Embodiments of three different methods of estimating TX IQMM using an envelope detector are described below in the context of the example embodiment illustrated in
Method 1
In some embodiments, this method may seek to obtain single-tap pre-compensator filter coefficients that may cancel IQMM at frequencies±f1, . . . , ±fK. These coefficients may then be used to estimate IQMM parameters ϕTX and VTX(f).
Referring to
The frequency response of the envelope detector output at frequency 2fk may be given by
R(f)|f=2fk=ATX2G*1TX(−fk)G2TX(fk). (9)
In the absence of IQMM, G2TX(fk) may be zero and thus R(2fk) in Equation (9) may become zero. By performing a search of pre-compensator coefficients, one-tap pre-compensator settings. i.e., wTX[n]=wTX,0×δ[n], may be obtained such that R(2fk) may become zero and cancel IQMM at frequency fk. After sweeping fk and obtaining the IQMC coefficients (e.g., optimal coefficients) over all frequency tones denoted by wTX,0opt(f) for TD=0, then ϕTX and VTX(f) may be estimated as follows for a CVC structure
In some embodiments, a search of pre-compensator coefficients may be implemented as an extensive or exhaustive search. For example, a search may be conducted over a wide range of pre-compensator settings and/or frequency tones at fixed intervals. In some embodiments, a search may be performed in stages. For example, an initial search may be conducted on a relatively coarse grid of pre-compensator settings and/or frequency tones over a wide range at wider intervals. One or more additional searches may then be performed on a finer grid at smaller intervals over one or more smaller ranges based on the results of the coarse search.
Method 2
In some embodiments, this method may estimate the IQMM parameters for a given frequency fk directly, for example, by sending single-tone signals at fk and −fk separately using two different pre-compensator coefficients and/or settings. The envelope detector outputs at frequency 2fk for these measurements may then be combined and solved using, for example, a quadratic equation in closed form to obtain the frequency-dependent gain and phase mismatches at fk. Then the IQMM parameters ϕTX and VTX(f) may be found, for example, as simple functions of the frequency-dependent gain and phase mismatches for each frequency fk.
Some example implementation details may be as follows. A single-tone signal at frequencies fk and −fk may be applied separately at BB to a TX path without any IQMC. e.g., WTX[n]=0, for the CVC architecture illustrated in
where J1 and J2 may be known values that may be defined as follows
J1=1,
J2=W*TX(−fk). (12)
Equations (11) may be reformulated using the relationship VTX(fk)=VTX(−fk) and Equations (2) and (3) as
Equations (13) may provide six real equations with five real unknowns, i.e., Re{γ}, Im{γ}, Re{VTX(fk)}, Im{VTX(fk)}, ϕTX, which may be solved to obtain estimates of VTX(fk) and ϕTX. IQMM parameter VTX(−fk) may be estimated as {circumflex over (V)}TX(−fk)={circumflex over (V)}*TX(fk), which may follow from hITX(t) and hQTX(t) being real-valued filters that may be conjugate symmetric in the frequency domain. i.e., HITX(f)=H*ITX(−f) and HQTX(f)=H*QTX(−f).
Method 3
In some embodiments, this method may involve sending two-tone pilot signals at frequencies fk
Referring to
Next, a multi-tone signal may be sent at frequencies fk
Then, a multi-tone signal may be sent at frequencies −fk
The following parameters may be defined:
Combining all of the observations may provide the following set of non-linear equations:
Y1,k=x1y1,
Y2,k=z1w1,
Y3,k=x1w1+y1z1,
Y4,k=x1z*1+y1w*1,
Y5,k=x1z2+y1w2,
Y6,k=x1w*2+y1z*2,
Y7,k=x2w2+y2z2,
Y8,k=x2z*2+y2w*2. (15)
This set of 8 equations with 8 unknowns in Equations (15) may be solved, for example, using the following steps:
1.
2. After obtaining all Tk
In some embodiments, fk1>0 and fk
The selection of two-tone pilot signals (and positive and negative frequencies thereof), as well as the resulting envelope detector output signals selected for analysis are for purposes of illustration only, and other combinations of pilot signals and/or output signals may be used. For example, in the second set of signals in
As described above, in some embodiments, one or more of the equations that may be obtained using method 3 may include one or more IQMM parameters of the two frequencies of a two-tone signal. In contrast, in some embodiments using method 2, each equation may only contain the IQMM of a single-frequency. Thus, in some embodiments, and depending on the implementation details, different sets of equations may be obtained using different methods.
In some embodiments, after obtaining estimates of ϕTX and VTX(f) for f=±f1, . . . , ±fK, these estimates may be used to compensate for FD-IQMM in the TX path. In some example embodiments, a least squares (LS) method may be implemented as follows: for a given delay element TD, the parameter WTXopt(f) given in Equation (4) may be estimated at frequencies f=±f1, . . . , ±fK. For example, in an embodiment having a finite impulse response (FIR) filter wTX[n]=Σi=0L-1wTX,iδ[n−i] of length L, the method may obtain the optimal L-tap filter wTX=[wTX,0, . . . , wTX,L-1]T∈L×1 that may minimize the least squared (LS) error between WTX(f) and ŴTXopt(f) at frequencies f=±f1, . . . , ±fK as
where Ŵopt=[ŴTXopt(−fK), . . . , ŴTXopt(−f1), ŴTXopt(f1), . . . , ŴTXopt(fK)]T and F=[F0, . . . , FL-1] is the discrete Fourier transform (DFT) matrix of size 2K×L. In some embodiments, TD may take values in {0, . . . , L−1}. For a fixed TD, wTX may be found as ŵTX,T
Although some techniques have been described in the context of pre-compensator structures such as the one illustrated in
In any of the embodiments disclosed herein, frequency domain signals (e.g., signals R1,k, . . . , R4,k in
At operation 1014, the method may increment the value of the counter k and return to operation 1004, where the method may check the value of the counter k. If k is greater than the maximum value K, the method may proceed to operation 1016 where, using the observations for R1,k, . . . , R4,k, ∀k, the method may estimate the IQMM parameters ϕTX and VTX(f), f=±f1, . . . , ±fK. At operation 1018, the method may use ϕTX and VTX(f), f=±f1, . . . , ±fK to estimate coefficients for the TX IQMM pre-compensator 418. The method may then terminate at operation 1020.
As mentioned above, in some embodiments. R1,k, . . . , R4,k may be obtained by capturing the time-domain signal at BB of the RX path 402 and converting it to a frequency-domain signal, for example, using an FFT.
At operation 1118, the method may increment the value of the counter k and return to operation 1104, where the method may check the value of the counter k. If k is greater than the maximum value K, the method may proceed to operation 1120 where, using the pre-compensation settings for ±f1, . . . , ±fk, the method may estimate the IQMM parameters ϕTX and VTX(f), f=±f1, . . . , ±fK. At operation 1122, the method may use ϕTX and VTX(f), f=±f1, . . . , ±fK to estimate coefficients for the TX IQMM pre-compensator 718. The method may then terminate at operation 1124.
At operation 1216, the method may increment the value of the counter k and return to operation 1204, where the method may check the value of the counter k. If k is greater than the maximum value K, the method may proceed to operation 1218 where, using Y1,k, Y2,k, and Y3,k, for every k, the method may estimate the IQMM parameters ϕTX and VTX(f), f=±f1, . . . , ±fK. At operation 1220, the method may use ϕTX and VTX(f), f=±f1, . . . , ±fK to estimate coefficients for the TX IQMM pre-compensator 718. The method may then terminate at operation 1222.
At operation 1318, the method may increment the value of the counter k and return to operation 1304, where the method may check the value of the counter k. If k is greater than the maximum value K, the method may proceed to operation 1320 where, using Y1,k, . . . , Y8,k, for every k, the method may estimate the IQMM parameters ϕTX and VTX(f), f=±f1, . . . , ±fK. At operation 1322, the method may use ϕTX and VTX(f), f=±f1, . . . , ±fK to estimate coefficients for the TX IQMM pre-compensator 718. The method may then terminate at operation 1324.
The operations and/or components described with respect to the embodiments illustrated in
This disclosure encompasses numerous inventive principles relating to association and authentication for multi access point coordination. These principles may have independent utility and may be embodied individually, and not every embodiment may utilize every principle. Moreover, the principles may also be embodied in various combinations, some of which may amplify the benefits of the individual principles in a synergistic manner.
The embodiments disclosed above have been described in the context of various implementation details, but the principles of this disclosure are not limited to these or any other specific details. For example, some functionality has been described as being implemented by certain components, but in other embodiments, the functionality may be distributed between different systems and components in different locations and having various user interfaces. Certain embodiments have been described as having specific processes, steps, etc., but these terms also encompass embodiments in which a specific process, step, etc. may be implemented with multiple processes, steps, etc., or in which multiple process, steps, etc. may be integrated into a single process, step, etc. A reference to a component or element may refer to only a portion of the component or element.
The use of terms such as “first” and “second” in this disclosure and the claims may only be for purposes of distinguishing the things they modify and may not indicate any spatial or temporal order unless apparent otherwise from context. A reference to a first thing may not imply the existence of a second thing. Various organizational aids such as section headings and the like may be provided as a convenience, but the subject matter arranged according to these aids and the principles of this disclosure are not limited by these organizational aids.
The various details and embodiments described above may be combined to produce additional embodiments according to the inventive principles of this patent disclosure. Since the inventive principles of this patent disclosure may be modified in arrangement and detail without departing from the inventive concepts, such changes and modifications are considered to fall within the scope of the following claims.
Nayebi, Elina, Dayal, Pranav, Song, Kee-Bong
Patent | Priority | Assignee | Title |
Patent | Priority | Assignee | Title |
10097396, | Aug 22 2014 | Texas Instruments Incorporated | TX IQ mismatch pre-compensation |
10225118, | Sep 22 2017 | Kabushiki Kaisha Toshiba; Toshiba Electronic Devices & Storage Corporation | Carrier leakage correction method for quadrature modulator |
10412698, | Feb 22 2017 | SAMSUNG ELECTRONICS CO , LTD | System and method for IQ mismatch calibration and compensation |
11240089, | May 15 2020 | Samsung Electronics Co., Ltd. | Methods and apparatus for transmit IQ mismatch calibration |
8184739, | May 21 2009 | NTT DoCoMo, Inc | Power series digital predistorter and control method therefor |
9231839, | Jul 07 2014 | MEDIATEK INC | Communication unit and method for determining and/or compensating for frequency dependent quadrature mismatch |
20090310711, | |||
20100195706, | |||
20160173317, | |||
20160294437, | |||
20160359614, | |||
20190380101, | |||
20200169342, | |||
20200169434, |
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